Z94.2 - Anthropometry & Biomechanics: Biomechanics Section

RADIAL DEVIATION. Movement of the hand which deflects its longitudinal axis toward the radius (q.v.). It causes the head of radius (q.v.) to press against the capitulum of humerus (q.v.) and may lead to irritation known as "tennis elbow." Tool design should minimize radial deviation. Strength of grasp is diminished in radial deviation.

RADIAL NERVE. One of the main nerves of the arm providing motor stimuli to extensor muscles of the forearm, wrist and fingers. Receives sensory feedback from back of forearm and hand.

RADIOCARPAL JOINT. Commonly known as the wrist, this joint provides all movements between the radius-ulna and hand. Because of its flexibility, the radiocarpal joint is often abused in adapting to the use of improperly designed tools.

RADIOHUMERAL JOINT. Part of the elbow which is thrust bearing. The site of tennis elbow (q.v.). Composed of the head of radius (q.v.) and capitulum of humerus (q.v.). (See RADIAL DEVIATION.)

RADIO-ULNAR JOINTS. The mechanism whereby the radius and ulna rotate about one another during pronation (q.v.) and supination (q.v.). At the elbow, the head of radius pivots in a notch in the ulna and is contained by an encircling annular ligament, thus forming a journal bearing. The bones are maintained in relative position by a ligamentous sheet connecting their central sections. During pronation and supination the distal end of the radius glides around the head of the ulna and rotates on its own axis. Workplace design should assure proper wrist and hand alignment during supination and pronation to avoid trauma. (See
RADIAL DEVIATION, TENNIS ELBOW.)

RADIUS. The long bone of the forearm in line with the thumb. It is the active element in the forearm during pronation (q.v.) and supination (q.v.). It also provides the forearm connection of the wrist joint. (See RADIOCARPAL JOINT, RADIOHUMERAL JOINT, ULNA.)

RANGE OF FOREARM PRONATION AND SUPINATION. The total useful rotational capability of the wrist about the longitudinal axis of the forearm. Very important in industrial tasks involving screwing actions, twisting motions, etc. Range (approximately 180 degrees) is greatest if no other deflection (ulnar or radial deviation) occurs at the same time.

RAYNAUD'S DISEASE. Constriction of the blood vessels of the hand from cold temperature, emotion, or unknown cause. Afflicts women predominantly and affects both hands simultaneously. Primary Raynaud's disease is believed to exist in 15% of the general population, and is hereditary and nonoccupational in nature. Occupational, or secondary Raynaud's Syndrome, is also referred to as vibration white finger, and is associated with excessive vibration with use of heavy, vibrating, and reciprocating hand tools, and working in cold temperatures. Hands become cold, blue and numb and lose fine prehensile (q.v.) ability. On recovery hands become red accompanied by burning sensation. Easily confused with one-sided numbness and tingling caused by poor tool design and resulting pressure. (See SCALENUS ANTICUS SYNDROME.)

REACTANCE PLATFORM (FORCE PLATFORM). A balance system for measuring forces or accelerations of a supported body. In biomechanics the force platform is used to measure the forces associated with movement and the accelerations associated with these forces. Used as inputs along with kinematic data in biomechanical models to determine joint loading during lifting or gait analyses. Shifts in the center of gravity of the total body can also be determined.

REACTIONS INVENTORY. The available physiological, kinesiological or psychological responses of an individual to a stimulus or set of stimuli. Reactions will vary with time and depend on the condition (preparedness, fatigue, etc.) of the individual.

RECTUS ABDOMINUS. Long strap-like muscle originating in the pubic region and running vertically to insert in the lower ribs and sternum. By contracting, it flexes the vertebral column and compresses the abdominal wall. It functions as the antagonist (q.v.) to the sacrospinalis (Erector Spinae (q.v.)). The rectus abdominis, by contracting can break the force of a blow to protect the abdominal viscera. However, workplace design should avoid repeated impact of the rectus abdominis.

REFERRED PAIN. Pain sensed at a place distant from its true origin (e.g., pain originating in stomach may be felt high in the lumbar region; e.g., pressure on the front of the abdomen may produce pain in the shoulder). Unawareness of referred pain patterns is frequent cause of incorrect identification of loci of work stresses.

REFLEX. (See SIMPLE REFLEX.)

REFLEX GONIOMETRY. Quantification of reflexive response by measurement of angular displacement, velocity and/or acceleration of a limb about a joint. Used in the evaluation of drug effects as related to safety at the workplace.

REHABILITATION. Treatment to restore a loss of capacity by retraining, medication, corrective exercise, or substitution of new faculties to replace those lost or damaged. Includes physical, emotional and technological rehabilitation.

RESPIRATION. Commonly called breathing. The composite process of internal respiration wherein an exchange of gases between circulatory fluids and cells occurs and external respiration which covers the gas exchange between blood and the air in the lungs. Respiration must occur to sustain life and must be adequate for efficient workplace function, i.e., the task should not interfere with normal breathing. Inadequate internal respiration is one of the causes of muscular fatigue. (See ANOXIA, ISCHEMIA, ANAEROBIC METABOLISM.)

RESPIRATORY QUOTIENT. The ratio of carbon dioxide volume exhaled to volume of oxygen up-take. Respiratory quotient varies considerably with type of foodstuff being metabolized and is increased by hyperventilation and acidosis. In steady work, the respiratory quotient is an index of work strain.

RESTING METABOLISM. Physiological combustion process usually expressed in units of oxygen consumed per unit time in a person at rest while seated or standing in normal position at the workplace. Increase in metabolic rate (q.v.) during specific activities above resting metabolism is the metabolic cost (q.v.) of the activity.

ROTATION. Motion in which all points describe circular arcs above an immovable line or axis.

ROTATOR CUFF. A group of muscles surrounding the shoulder joint, Because of the many components of available movement at the shoulder, it is susceptible to self-generated trauma caused by actions of the muscles of the rotator cuff. In the industrial setting, rapid reversals of movement in the shoulder should be minimized to avoid trauma or fatigue which may result.